Examples of procedures that require repeated access to anatomical vessels include dialysis and the delivery of medicines for an extended period of time. The multiple punctures that such repeated access necessitates eventually render the accessed vessels unsuitable for further effective injections. Accordingly, there is a need for apparatus, methods, and systems for facilitating long-term, repeated vascular access.
Dialysis procedures, for example, typically employ catheters, which are inserted into a patient's bloodstream to withdraw blood for treatment and then return treated blood back into the bloodstream. However, there are a number of drawbacks to such catheter systems. For example, because the catheters of such systems are inserted directly into the lumen of a patient's blood vessel, they obstruct blood flow in the vessels. Therefore, the diameter of catheters available for dialysis is quite limited. A dialysis catheter must be sufficiently small to allow for a relatively smooth path for blood flow around the catheter. Because high flow rates through catheters are desirable to maximize the efficiency of dialysis procedures, this limitation is disadvantageous.
Dialysis procedures and systems utilizing catheters have a number of other disadvantages. For example, because the catheters of such systems are inserted directly into a patient's bloodstream, they are susceptible to developing thrombi, infection, and/or other complications. In addition, prior to each treatment with a conventional catheter dialysis system, the patient's skin and blood vessel must be punctured in one or more locations. These repeated punctures can damage a patient's blood vessels to the extent that they can no longer withstand further punctures. Also, repeated punctures of a patient's skin can be painful and can likewise damage the skin. Moreover, because the repeated use of larger needles and catheters causes greater damage to a patient's blood vessels and skin, this further limits the effectiveness of conventional dialysis procedures.
One solution to the need for repeated access which does not employ intraluminal catheters is disclosed in U.S. Pat. No. 3,826,257 issued to Buselmeier. Buselmeier discloses a percutaneous vascular access device utilizing a U-shaped shunt tube, the ends of which are anastomosed in an end-to-end manner to the severed ends of an artery and adjacent vein. The other ends of the artery and vein are tied off and allowed to become non-functional.
There are numerous drawbacks and disadvantages to the Buselmeier device, some of which will now be discussed. First, in Buselmeier, blood flow in the shunt tube is constantly exposed to foreign or non-native surfaces which are not easily replaceable—i.e., not without further recurring surgical procedures. Because there is such a large non-native surface area exposed to blood flow in the vessel, and because those surfaces that are exposed are not easily replaceable, the Buselmeier device is prone to complications such as thrombosis, blood stagnation, and infection. The only way to prevent or control such complications would be to replace the device, which requires an invasive surgical procedure. A replacement surgery would be needed on a more frequent periodic basis than would be practical. Moreover, the surgeries themselves tend to cause trauma to the vessels being accessed, which may ultimately leave them unsuitable for further access. For at least these reasons, the Buselmeier configuration is not suitable for effective long-term vascular access.
In addition, the Buselmeier device has blood from an artery re-routed directly into a vein. The characteristics of the fluid flow in an artery are significantly different from the characteristics of the fluid flow in a vein. These fluid flow dissimilarities may lead to additional adverse effects that detrimentally affect the long term accessibility of the blood vessels that must be accessed for the external blood treatment to be effectively performed. For example, in an arterio-venous (AV) graft constructed as a vascular access for dialysis, the blood flow and blood pressure characteristic of the arterial circulation are so different from the blood flow and blood pressure in the vein into which the blood of the AV graft flows that the vein usually develops hyperplasia and stenoses. Because of these fluid flow dissimilarities, it is preferable to avoid the detrimental impact on the vessels and their long-term accessibility caused by the Buselmeier configuration, even apart from the persistent surgical procedures needed to avoid the blood-flow complications discussed above.
It is therefore desirable to provide devices, systems, and methods that permit repeated access to a blood vessel or other anatomical vessel for external treatment, such as hemodialysis, in such a way that the vessel being accessed is available for successive dialysis operations. Moreover, it is desirable, particularly from a patient's perspective, to provide such devices, systems, and methods wherein access to a blood vessel is obtained without the need for puncturing the patient's skin and blood vessels each time access is needed.
It is also desirable to provide devices, systems and methods that permit repeated access to a blood vessel for the purpose of delivering medicines into the patient's blood stream in such a way that the receiving blood vessel is not so severely damaged that it cannot be used after a few administrations of medicine.
Furthermore, it would be desirable to provide a device that is suitable for repeated vascular access for the purpose of long term medicine delivery into the patient's blood flow and also for the purpose of effectively practicing hemodialysis for a long period of time. It would also be advantageous to provide such a device that can be connected to any of several veins and/or arteries or a combination thereof as desired. In addition, it would be desirable to provide such a device or system wherein the hemodialysis procedure could be completed without obstructing the flow of blood in the patient's bloodstream and thereby limiting the diameter of available tubes for blood transport.
The practical advantages of such devices and systems would be considerably enhanced if the device or system is reliably attachable to a blood vessel. These goals should be accomplished while minimizing, or avoiding to the maximum extent possible, undesirable adverse effects such as vessel thrombosis, blood stagnation, the formation of undesirable blood disturbances, and infection. Such complications are minimized by providing a configuration designed to minimize the exposure of the blood stream to non-native materials between accesses and can be further minimized by providing a configuration wherein the only non-native surface area exposed to blood flow is replaceable.
The prior art has yet to provide an apparatus or system having the desirable characteristics discussed above. Accordingly, there is a need for methods and apparatus that provide for repeated vascular access while minimizing the problems which are associated with those of the prior art.